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Don't call type_of on TAIT in defining scope in new solver

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This commit is contained in:
Michael Goulet 2023-06-28 17:41:04 +00:00
parent 87c8c83ec7
commit 388c230cf7
6 changed files with 67 additions and 101 deletions
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2
compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
View file

@ -837,7 +837,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
}
}
pub(super) fn can_define_opaque_ty(&mut self, def_id: LocalDefId) -> bool {
pub(super) fn can_define_opaque_ty(&self, def_id: LocalDefId) -> bool {
self.infcx.opaque_type_origin(def_id).is_some()
}

27
compiler/rustc_trait_selection/src/solve/trait_goals.rs
View file

@ -7,6 +7,7 @@ use rustc_hir::{LangItem, Movability};
use rustc_infer::traits::query::NoSolution;
use rustc_infer::traits::util::supertraits;
use rustc_middle::traits::solve::{CanonicalResponse, Certainty, Goal, QueryResult};
use rustc_middle::traits::Reveal;
use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams, TreatProjections};
use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt};
use rustc_middle::ty::{TraitPredicate, TypeVisitableExt};
@ -118,6 +119,32 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
return result;
}
// Don't call `type_of` on a local TAIT that's in the defining scope,
// since that may require calling `typeck` on the same item we're
// currently type checking, which will result in a fatal cycle that
// ideally we want to avoid, since we can make progress on this goal
// via an alias bound or a locally-inferred hidden type instead.
//
// Also, don't call `type_of` on a TAIT in `Reveal::All` mode, since
// we already normalize the self type in
// `assemble_candidates_after_normalizing_self_ty`, and we'd
// just be registering an identical candidate here.
//
// Returning `Err(NoSolution)` here is ok in `SolverMode::Coherence`
// since we'll always be registering an ambiguous candidate in
// `assemble_candidates_after_normalizing_self_ty` due to normalizing
// the TAIT.
if let ty::Alias(ty::Opaque, opaque_ty) = goal.predicate.self_ty().kind() {
if matches!(goal.param_env.reveal(), Reveal::All)
|| opaque_ty
.def_id
.as_local()
.is_some_and(|def_id| ecx.can_define_opaque_ty(def_id))
{
return Err(NoSolution);
}
}
ecx.probe_and_evaluate_goal_for_constituent_tys(
goal,
structural_traits::instantiate_constituent_tys_for_auto_trait,